Impact of Organophosphate Xenobiotic Ethion ( EC 50%) on Cell Viability, Behavior, Genetic Impairment, and Histoarchitecture in Cyprinus carpio

This study aimed to evaluate the cytotoxic, genotoxic, behavioral, and histological effects of the organophosphate insecticide ethion on common carp fingerlings (Cyprinus carpio, 10 ± 2 g). Short-term acute bioassays and subsequent confirmatory definitive tests were conducted, revealing the 96 h LC₅₀ of ethion to be 43.76 μ/L using Finney's probit method. Fish were treated to four sub-lethal concentrations (C₁ = 0.56 μ/L, C₂ = 0.8 μ/L, C₃ = 1.13 μ/L, C₄ = 2.3 μ/L) for the durations of 14 and 21 days. Ethion exposure resulted in a considerable concentration-dependent loss in cell viability and an elevation in necrotic and apoptotic cell populations. The frequency of micronuclei in hematocytes drastically increased (p < 0.05), suggesting the genotoxic potential of ethion in fish. Fish displayed dose- and time-dependent behavioral abnormalities following sub-lethal exposure to ethion, characterized by increased mucus secretion, convulsions, loss of balance, bleeding, and symptoms of muscle tetany. The pesticide caused histological abnormalities that intensified with concentration: modest lifting and fusing of gill lamellae at lower levels; degeneration and vasodilation at C₃; and severe lamellar and hepatic damage at C₄. Liver tissues demonstrated increasing vacuolation and degenerative changes, accompanied by nuclear hypertrophy and karyolysis at higher concentrations. The data reveal that ethion is particularly detrimental to common carp, generating cellular, genetic, behavioral, and tissue-level alterations that may imperil aquaculture populations if left uncontrolled.